Ordinary removable dentures, dental plates, and the like, comprise teeth mounted in a suitable plate or base. Dentures function as a substitute for missing teeth and serve as a replacement for all or a portion of the teeth ordinarily found in the oral cavity. Although dentures generally are skillfully prepared, often they do not fit perfectly. Moreover, no matter how satisfactory at first, after a period of time the fit of the denture becomes loose and imperfect due to natural shrinkage and changes in the gums, mucous tissues, and the like. Loose and imperfectly fitted dentures usually are corrected and stabilized by the use of a denture stabilizer. Denture stabilizers are used to fill the interstices between the dentures and the gums or tissues. Prior to placement of the denture in the oral cavity, a denture stabilizer is applied to the denture-plate surface which, for a perfect fit, should uniformly contact the gums and mucous tissues. The denture stabilizer is formulated not only for its adherent properties, but also to provide a cushion or gasket between the denture and the gums or tissues, thereby positioning the denture securely in the oral cavity.
Requirements and characteristics for a satisfactory denture stabilizing composition are many and are dictated by numerous factors. Desirably, one daily application of such a composition should function as an effective means for insulating, cushioning, and securely positioning the denture. The composition should retain its characteristics and properties in the typical powder and cream forms during storage under various climatic conditions such as high temperature and humidity; be readily and easily capable of application to the denture surface; not be irritating or uncomfortable to the user; be safe and nontoxic; have no disagreeable odor or color; have no unpalatable taste; optionally provide antiseptic and germicidal properties for preventing or inhibiting the growth of organisms ordinarily found in the mouth; and function as an agent for prevention of putrefaction or malodorous decomposition of foods or secretions lodging beneath or adjacent to the denture. The stabilizing material must be capable of imbibing water and saliva and swelling, so as to fill the interstices between the denture and the gum or mucous tissues. The stabilizer should not attack or damage the denture, as by causing a crazing of the denture-plate material. Additionally, the stabilizer should be stable to bacteria, molds and enzyme systems found in the oral cavity, and have a pH that is nonirritating to the oral mucosa, generally 5-8.5, preferably a pH around neutrality. The mechanical strength of the stabilizing mass, be it gel or colloid, formed by imbibition of water should be great enough to securely maintain the position of the denture under normal use, and not so great as to make denture removal difficult when desired, or as to damage or injure the gums, tissues or denture upon removal.
There has been a considerable effort made over many years to develop improved denture adhesives. Both synthetic and natural polymers and gums have been used singly, in combination, and in combination with various additives.
European Patent 64,672 to Dhabhar and Schmidt, published Nov. 17, 1982, relates to a hydrophilic denture adhesive containing an adhesive polymeric fraction comprising carboxymethylcellulose (CMC) and polyethylene oxide in a hydrophilic vehicle.
European Patent Application 140,486 to A. J. Desmaris, filed Jul. 31, 1984 relates to denture adhesive compositions containing a hydrophobically modified water-soluble polymer, alone or admixed with an alkali metal salt of CMC. Hydrophobically modified hydroxyalkyl celluloses and copolymers of ethylene oxide and long chain epoxyalkanes are preferred for use in the compositions.
U.S. Pat. No. 4,280,936 to Dhabhar, Heyd and Schmidt, issued Jul. 28, 1981, relates to improved denture adhesives containing a specified ratio of CMC and polyethylene oxide in a mineral oil base.
U.S. Pat. No. 4,474,902 to Dhabhar and Schmidt, issued Oct. 2, 1984, relates to improved denture adhesives containing karaya gum in a hydrophilic vehicle. See also U.S. Pat. No. 4,514,528, issued Apr. 30, 1985, and U.S. Pat. No. 4,518,721, issued May 21, 1985 to these same inventors, relating, respectively, to improved denture adhesives containing adhesive polymeric fractions consisting of admixtures of partial salts of lower alkyl vinyl ether maleic anhydride-type copolymers with CMC or polyethylene oxide, as well as denture adhesives containing CMC and polyethylene oxide. See also U.S. Pat. No. 4,522,956, issued Jun. 11, 1985 to Dhabhar and Schmidt relating to improved denture adhesives containing polyethylene oxide as the sole adhesive component in a hydrophilic vehicle comprising certain polyethylene glycols.
Other denture adhesives are described in U.S. Pat. No. 4,530,942, issued Jul. 23, 1989; U.S. Pat. No. 4,542,168, issued Sep. 17, 1985; and U.S. Pat. No. 4,569,955, issued Feb. 11, 1986.
U.S. Pat. No. 4,529,748 to H.G.P. Wienecke, issued Jul. 16, 1985, relates to dental prosthesis adhesives formed from film-forming substances such as various cellulose derivatives, acrylate polymers, methacrylate polymers, and other film-providing substances.
U.S. Pat. No. 4,138,477 to Gaffar, issued Feb. 6, 1979 discloses oral compositions to control mouth odor containing zinc-polymer combinations formed from zinc reacted with an anionic polymer containing carboxylic, sulfonic and/or phosphonic acid radicals.
U.S. Pat. No. 3,003,988, to D. P. Germann et al., issued Oct. 10, 1961, describes certain water-sensitized, but water-insoluble, materials for stabilizing dentures which are synthetic, hydrophilic, colloidal materials comprising mixed partial salts and esters of lower alkyl (1 to 4 carbons) vinyl ether-maleic anhydride-type copolymers, said mixed partial salts and esters containing both divalent calcium and monovalent alkali (i.e., sodium, potassium and ammonium) cations.
U.S. Pat. No. 4,758,630 to Shah et al., issued Jul. 19, 1988 relates to zinc and strontium partial salts of lower alkyl (C.sub.1 to C.sub.4) vinyl ether-maleic acid copolymers, wherein said zinc and strontium cations are "unmixed" with any other cations or ester functions in the copolymeric salt, the remaining initial carboxyl groups being unreacted. These lower alkyl vinyl ether-maleic acid copolymers are referred to hereinafter by the abbreviated term "AVE/MA copolymer" and the methyl vinyl ether-maleic acid copolymer as "MVE/MA copolymer". Further, European Patent Application 396,411, to Holeva and Gounaris published Nov. 7, 1990, discloses mixed partial MVE/MA copolymer salts.
It is known, therefore, that combinations of mixed and unmixed partial salts of lower alkyl vinyl ether-maleic anhydride-type copolymers are useful as denture adhesive compositions.
Yet, the search continues for denture stabilizers that will provide the above-described characteristics and, importantly, will maintain the secure fit of the denture over prolonged periods (10-14 hours) without the need for reapplication.
In accordance with the present invention, improved adhesive and other characteristics are obtained in a denture stabilizing composition by using specific single mixed partial salt(s) of a lower alkyl vinyl ether-maleic acid copolymer. The copolymers have a specific level of zinc (or strontium) cations, i.e., below about 9.9%.
It is an object of the present invention to provide improved denture stabilizers which are easy to manufacture and that will be stable over prolonged periods in the oral cavity, yet will allow easy removal of the denture on demand.
It is a further object of the present invention to provide denture compositions which provide the user with improved sensory, such as flavor, benefits.
It is a further object to provide such stabilizers using toxicologically-acceptable, palatable materials.
It is another object herein to provide stabilizers that perform well in the presence of moisture, particularly in the presence of body fluids such as saliva, perspiration and blood.
These and other objects are secured by the present invention, in the manner disclosed hereinafter.